DIY Linn T Kable - Tonearm Cable

[jagdesign]

I'm making a new cable for my Ittok, using Mogami 2549, which I understand is what Linn use on the T-Kable.

I just want to confirm the ground/shield arrangement. At the moment I'm thinking the centre pin of the DIN plug connects to a separate ground wire, which splits to allow a connection to the sub-chassis, and to my phono stage ground post.

So my question is what to do (if anything) with the Mogami shield on each L and R cable? Leave it floating or connect to the signal return at one end on each RCA plug?

Would like to follow the T-Kable construction where possible. Ta

 

[Craig B]

If T-Kable RCA is Mogami 2549 mic cable then they will have had to connect both signal -ve and shield to RCA -ve (outer ring) else the cable not be shielded. This would also tie in with Linn's LinnDocs "Converting XLR to/from Phono/RCA" connection method (at least at the RCA end). Best to leave shield disconnected from DIN pin 2 (ground) at the arm plug end, else increase the potential (no pun intended) of a ground loop and/or RF issues via the dedicated ground wire. Either that, or omit a dedicated ground wire to amp altogether, and connect both shields to DIN pin 2 with a short ground lead to Linn chassis. WRT the latter, I notice that T-Kable XLR does not include a dedicated ground wire to amp nor a short ground lead to chassis, likely just a standard shield to XLR pin 1, signal +ve to pin 2, and signal -ve to pin 3 pattern, no doubt with both shields connected to DIN pin 2.

From 'Cables and Terminations' [credit: LinnDocs]:

 

[jagdesign]

Thanks @Craig B

That makes sense to me.

- Mogami shield(s) connected to RCA -ve along with the primary -ve conductor.

- Separate ground wire connected to DIN arm plug, pin 2, with connections back to sub-chassis , and pre amp ground post.

The only thing I’ve read which contradicts this slightly, is many posts elsewhere mentioning to connect the interconnect shields at source end only?

 

[Chops54]

The only thing I’ve read which contradicts this slightly, is many posts elsewhere mentioning to connect the interconnect shields at source end only?

I think that applies mostly for rca to rca interconnects.

 

[Craig B]

Thanks @Craig B

That makes sense to me.

- Mogami shield(s) connected to RCA -ve along with the primary -ve conductor.

- Separate ground wire connected to DIN arm plug, pin 2, with connections back to sub-chassis , and pre amp ground post.

The only thing I’ve read which contradicts this slightly, is many posts elsewhere mentioning to connect the interconnect shields at source end only?

You're welcome.

When talking about quasi-balanced grounding/shielding schemes my brain wants to think of where the ultimate ground plane junction is rather than source vs. amp.

Regardless, in this particular scenario, I'd say good luck to anyone trying to connect 2 x braided shield wire plus ground wire to pin 2 in DIN5. Even if Linn's custom mic cable features an additional drain wire running through the shield, getting three twisted/tinned together and soldered into the middle of 5 x DIN pins has to be the definition of cruel and unusual punishment for any cable tech.

Of course, T-Kable XLR sans dedicated ground lead(s) must have the 2 x shields connected to DIN pin 2 at arm connector end. Perhaps their OEM cable is a custom job with shield drain leads within (an uninsulated wire that runs end to end in contact with the shield, with the braided shield simply cut short with the outer insulator, leaving the shield drain wire as single connection to ground pin or tab).

Getting back to T-Kable RCA, I don't see it being a case of which end the shield connects to, more a case of the signal conductors being fully enclosed within ground connected metal, braided and/or solid, along the full signal path. At the tonearm end the DIN socket gets firmly planted within a large grounded metal cylinder (aka the tonearm pillar), whereas, at RCA end the shield connected plug has a conductive metal barrel screwed on over the otherwise exposed signal wire ends.

Has anyone dared unscrew their T-Kable either end?

 

[Paul R]

I don't know how a T-Kable is wired.

But I would try using the two screens of the signal cables to replace the separate earth wire and connect both to the preamp earth tag. Perhaps as has been done in the XLR terminated T-K. Keep the cartridge floating until the phono pre decides to make the 0v connection rather than forcing it in the cabling.

 

[Craig B]

I don't know how a T-Kable is wired.

But I would try using the two screens of the signal cables to replace the separate earth wire and connect both to the preamp earth tag. Perhaps as has been done in the XLR terminated T-K. Keep the cartridge floating until the phono pre decides to make the 0v connection rather than forcing it in the cabling.

This is sort of the point of quasi- or pseudo-balanced RCA shod mic cables in that the shield is only connected at one end and therefore does not act as 0V connection between two components.

What intrigues me is the XLR shod T-Kable variant, as Linn appear to be leaving the ground path of LP12 top plate, wiring strap, and sub-chassis strictly over on the mains earth side.

 

[Paul R]

I wonder if the arm base earth strap has been painted out of the Linn T-Kable XLR photo?

More interestingly. For DIY, what arm base plug? Everything else is easy.

 

[Craig B]

I wonder if the arm base earth strap has been painted out of the Linn T-Kable XLR photo?

If so, then they've also done a good job of hiding it within the retail packaging.

More interestingly. For DIY, what arm base plug? Everything else is easy.

This one, used by Jelco in their JAC-502 cable, is one of the few right angle ones I've seen that can clamp 2 x thickish insulated leads in. LPGear have it listed as 'Zupreme Phono DIN Connector'. They have the cable entrance dimensions down as 11 x 5mm but seeing as how the screw-on bottom forms half of this it should be possible to persuade 2 x 6mmØ Mogami to fit. I see that Analog Seduction has something similar in silver/grey finish branded as Atlas.

 

[Cloth Ears]

@jagdesign I think I have some pics of the din plug with the lid off and each phono plug with the covers removed. I was considering making one once but then bought an Ekos SE with latest T Cable.

I will see if I can find them for you.

 

[Paul R]

If so, then they've also done a good job of hiding it within the retail packaging.

Indeed they did. Which does beg a question about that internal link between shields.

This one, used by Jelco in their JAC-502 cable, is one of the few right angle ones I've seen that can clamp 2 x thickish insulated leads in. LPGear have it listed as 'Zupreme Phono DIN Connector'. They have the cable entrance dimensions down as 11 x 5mm but seeing as how the screw-on bottom forms half of this it should be possible to persuade 2 x 6mmØ Mogami to fit. I see that Analog Seduction has something similar in silver/grey finish branded as Atlas.

Interesting, and not completely stupidly priced.

i have a very, very early Ekos with original cable. I think the practice was to remove the removeable part of the plug and fill the void with Araldite. Need to take the bottom off the turntable and have a look, see if my recollection is correct.

And I have an Alphason Xenon with VdH wiring that looks like it might be twisted pair, so I'll take a look inside. This arm cable isn't removeable and has the earth strap for the LP12 chassis. Some years ago I rewired an RB300 with twisted pair from the arm base into phonos and wired the earths as I suggested up thread. Seems to work. Cable is green which is the critical thing.

 

[jagdesign]

Thanks for all the comments guys. I’ve gone ahead and built it with the shield just connected at the RCA ends.

Will post some pics and details of the DIN plug I used at a sensible hour tomorrow!

 

[jagdesign]

So this is the plug I used

I doesn't fit the standard Mogami 2549 OD (x2) so I trimmed the ends and excess shields, then heatshrinked

Then soldered the DIN, including the two ground wires.

Then the Neutrik Profi RCAs

Plug and cables shouldn't foul the base board (assuming it has a hole where the tonearm is situated), but I'm not using the baseboard

And how it's currently dressed, think I need to play around with this a bit for optimal bounce

I won't be able to comment on SQ improvements as I only built this cable due to the existing Ittok one being too short!

 

[Cloth Ears]

I found the pics of the genuine T cable but unfortunately the all important one of the din connector is not very clear. I think these came from the Lejonklou forum if I remember correctly.

There is also a useful truth table in Excel comparing the new cable with the old Ittock pinout but I cannot guarantee the accuracy of this and of course it does not really tell you which end connections are made.

The first one confirms the thin earth with a spade connector goes directly to the din connector and that must be pin 3.

The next one shows the din connector and it confirms the signal wires use the clear conductor and the earth returns use the blue conductors
There is a soldered connection to pin 3 which must be the thin earth connection but it is very difficult to see how the screens are connected if at all.

The next one shows the Phono plugs and it is easy to see the clear conductor going to the main pin, the blue conductor to one side of the body and the screen going to the other side of the body.

The final one is a screen shot of the Excel table showing continuity between the various points. I have looked at this many times and come up with a different answer every time.

I may be a touch late as I see you have already made your cable but hopefully the above may help.

 

[jagdesign]

That's really interesting @Cloth Ears, thanks.

It looks like the Mogami shield(s) are connected to DIN pin 3, but the original Ittok cable doesn't (possibly doesn't use a screened/shielded cable)? Also interesting that the T-Kable does away with the sub-chassis ground connection.

Funny that I chose blue for the +/centre pin

 

[Craig B]

That's really interesting @Cloth Ears, thanks.

It looks like the Mogami shield(s) are connected to DIN pin 3, but the original Ittok cable doesn't (possibly doesn't use a screened/shielded cable)? Also interesting that the T-Kable does away with the sub-chassis ground connection.

Funny that I chose blue for the +/centre pin too

The old Linn tonearm cable was the usual co-axial type with the centre core carrying signal +ve and the shield carrying signal -ve. Interestingly, the Excel table above indicates that DIN pins 4 and 5* (Lch -ve and Rch -ve) are strapped within.

Zooming in on the open Linn DIN pic, it appears that they've strapped pins 4 (Lch -ve) and 5 (Rch -ve) to pin 2 (ground)*. This would make the 'New Cable (Mogami T Kable)' continuity table correct. It does appear that there are two dedicated tonearm ground wires exiting the Linn DIN (i.e. you can just make out the one passing the other in the first pic).

From the above, I think we can safely conclude here that within the Linn Products Cable Dept. there is no such thing as too many ground paths.

Regardless, the bottom line here is whether or not one's DIY cable is nice and quiet. It certainly appears that you've done a nice soldering job. Hopefully, I haven't given you a bum steer with the quasi-balanced guess wrt the shields being connected at RCA end only.

* Being ever the diehard pedant, I'm using the actual DIN pin numbering here. From top right in the Excel pic these are 1, 4, 2, 5, 3 (female mating socket side/male solder bucket side).

DIN5 180º or 240º pin numbers (female mating side/male wiring side):

 

[Cloth Ears]

@Craig B I would agree 100% with using the correct Din plug numbering as you show above.

Ground is always pin 2 on 3 pin and 5 pin Din connectors. I only referred to pin 3 being ground to tie in with the Excel table above sorry for any confusion.

That's really interesting @Cloth Ears, thanks.

Also interesting that the T-Kable does away with the sub-chassis ground connection.

I think the first pic I posted was a bit misleading, The thin wire leaving the Din plug and heading off to the right is the sub-chassis ground.
Here is a better picture. The long thin wire goes into the Din plug and a short wire leaves to the chassis both connected to the central earth pin in the Din plug - just as you have made yours.

The more I think about it the more unlikely it is that the two screens are connected to the earth pin in the Din plug as this would be creating a perfect hum loop.

 

[jagdesign]

Well, I can confirm it’s all sounding pretty bloody great, no hum/grounding issues that I can make out, and well, I can see why my dad’s had his LP12 for 30ish years.

Thanks for all the input - hope others find it useful

 

[Craig B]

@Craig B I would agree 100% with using the correct Din plug numbering as you show above.

Ground is always pin 2 on 3 pin and 5 pin Din connectors. I only referred to pin 3 being ground to tie in with the Excel table above sorry for any confusion.

No worries. It was I who was creating confusion by being so pedantic as to correct the Excel numbering.

The more I think about it the more unlikely it is that the two screens are connected to the earth pin in the Din plug as this would be creating a perfect hum loop.

If the Excel continuity table is correct then the screens must be connected to earth, albeit indirectly. They've listed pins 2, 4, and 5 (DIN numbering convention) all as showing continuity with both flying earth wires, and RCA Rch -ve, and RCA Lch -ve.

We know that the Mogami screens are common to both RCA Rch -ve and RCA Lch -ve, therefore, assuming the Excel continuity table to be correct, both screens must be connected to pin 2, even if indirectly so.

 

[tomek]

Linn is using Mogami 2549, Jelco is (was ...) using 2534 for their tonearm cables . I tried both and IMHO 2534 is much better sounding cable ...